Government figures show robocall complaints up about 225 percent since late 2010. The spike raises questions about how well the federal do-not-call list is working. That list bars telemarketers from calling the more than 209 million phone numbers on the registry.

The Federal Trade Commission says the registry is doing an effective job fighting unwanted sales calls. The FTC does acknowledge that robocalls have become a bigger problem in recent years. The calls are hard to trace because scammers use caller-ID spoofing to mask their phone number.